A conventional heat exchanger includes a core portion in which tubes and corrugated fins are stacked alternately. A tank is disposed on an end part of the tubes in a tube longitudinal direction. The tank includes a core plate to which the tubes are inserted, and a tank body portion fixed to the core plate to define an inner space of the tank together with the core plate.
The core plate includes: a flat body portion having a flat surface on an inner side of the tank, and tube holes through which the tubes are inserted; and a groove portion provided on an outer edge of the flat body portion. An end part of the tank body portion is inserted into the groove portion. The core plate has a rib protruding from the flat body portion outward of the tank and extending in a core plate-width direction in order to enhance stiffness in the core plate-width direction.
In a heat exchanger described in Patent Document 1, such rib overlaps an end part of tubes in a tube stacking direction over and is disposed such that a flat part coplanar with the a flat body portion is present on an inner side of a tank between the rib and a groove portion. This rib is formed by press forming.
Since the rib superior in stiffness overlaps the end part of the tubes, the stiffness with respect to the core plate-width direction in vicinity of the end part of tubes can be improved. On the other hand, the flat part provided between the rib and the groove portion is easy to be deformed. Thus, when a thermal stress is generated to make the core plate arch in a tube longitudinal direction, the thermal stress can be absorbed by deformation of the flat part. Consequently, compared with a heat exchanger in which a rib and a groove portion are in contact with each other without a flat part between the rib and the groove portion contrary to the heat exchanger described in the Patent Document 1, stress concentration on a tube base part that is a connection part between tubes and the core plate can be reduced when a temperature difference is generated between the tubes.